[Federal Register Volume 64, Number 194 (Thursday, October 7, 1999)]
[Notices]
[Pages 54651-54653]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-26143]
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NUCLEAR REGULATORY COMMISSION
I
Entergy Operations, Inc. (Arkansas Nuclear One, Unit 2);
Exemption
[Docket No. 50-368]
Entergy Operations, Inc. (the licensee), is the holder of Facility
Operating License No. NPF-6, which authorizes operation of Arkansas
Nuclear One, Unit 2. The license provides, among other things, that the
licensee is subject to all rules, regulations, and orders of the
Commission now or hereafter in effect.
The facility is one of two pressurized-water reactors at the
licensee's site located in Pope County, Arkansas.
II
In its letter dated October 8, 1997, as supplemented by letter
dated February 25, 1999, the licensee requested an exemption from the
Commission's regulations. Title 10 of the Code of Federal Regulations
(10 CFR), Part 50, Appendix R, Section III.G.2, is designed to ensure
that adequate fire protection features are provided for redundant
cables or equipment located in the same fire area outside of primary
containment such that at least one of the redundant trains of safe
shutdown equipment will remain available during and after any
postulated fire in the plant to achieve and maintain safe shutdown
conditions. Section III.G.2.c requires the following means of
assurance:
Enclosure of cable and equipment and associated non-safety
circuits of one redundant train in a fire barrier having a
1-hour fire rating. In addition, fire detectors and an automatic
fire suppression system shall be installed in the fire area[.]
The licensee has requested an exemption from the requirements of 10
CFR Part 50, Appendix R, Section III.G.2.c, for cables and equipment
located below the 354-foot elevation of the ANO-2 intake structure. The
licensee is requesting an exemption from the specific requirement to
provide fire detectors and an automatic fire suppression system to
protect redundant trains of safe shutdown equipment that are located in
the same fire zone. The licensee has demonstrated that one redundant
train of cable and equipment, required to achieve and maintain safe
shutdown conditions, is protected with a fire barrier having an
equivalent 1-hour fire rating.
III
Pursuant to 10 CFR 50.12, the Commission may, upon application by
any interested person or upon its own initiative, grant exemptions from
the requirements of 10 CFR Part 50 (1) when the exemptions are
authorized by law, will not present an undue risk to public health or
safety, and are consistent with the common defense and security; and
(2) when special circumstances are present. Special circumstances are
present whenever, according to 10 CFR 50.12(a)(2)(ii), ``Application of
the regulation in the particular circumstances would not serve the
underlying purpose of the rule or is not necessary to achieve the
underlying purpose of the rule * * *''
The underlying purpose of 10 CFR Part 50, Appendix R, Section
III.G.2, is to provide reasonable assurance that at least one of the
redundant trains of safe shutdown equipment will remain available
during and after any postulated fire in the plant to achieve and
maintain safe shutdown conditions.
The ANO-2 intake structure is about 32 feet by 26 feet on three
levels. There are no rated fire barriers between the three levels.
Below the 354-foot elevation there are three intake bays, which contain
service water (SW) piping and conduits. The bays are approximately 7
feet by 32 feet and are separated from one another by 2-foot thick,
non-rated concrete walls. The bays are separated from the ground level
by an 18-inch thick, non-rated concrete slab on metal decking. The
floor of the bays is typically covered with water 16 feet deep. The
ceiling height is approximately 14 feet above the normal pool level. Of
the three bays, only the ``A'' SW intake bay contains redundant cables.
The licensee stated that the total in-situ combustible loading is
3,469,060 BTUs, which is equivalent to a fire severity to a standard
fire duration of less than 4 minutes. Each bay is administratively
controlled as a ``confined space,'' thus limiting access by personnel
during routine operations and precluding the accumulation of
combustibles. In addition, the licensee's administrative procedures
limit the transient combustibles to 5 pounds unless personnel are
continuously present in the area. In such cases, the personnel could be
either the craft personnel responsible for using the combustible
materials or a continuous fire watch. Water to the bay is normally
provided through a sluice gate for the bays where the circulating pumps
take suction.
SW is required to be available to supply cooling water for various
safe shutdown components including the diesel generators and the
shutdown cooling heat exchangers. Additionally, SW can be aligned to
the emergency feedwater system in the event that the desired condensate
source is depleted. The time critical function is to supply cooling for
the diesel generators. The licensee stated that, on the basis of its
calculations, the diesel generators (and therefore the SW system
components) are not required to be operated during the first 30 minutes
of a postulated fire event. The licensee allows the operators to
manually align the SW system because the diesel generators are not
required during the first 30 minutes of a fire event and sufficient
time is available to complete the alignment.
[[Page 54652]]
The SW system consists of two independent seismic category 1 flow
paths, which furnish cooling water to two independent trains of 100
percent capacity engineered safety feature equipment, and two
nonseismic category 1 flow paths. The SW system has three 100 percent
capacity pumps. One pump is dedicated to each of the two SW trains
while the third pump is designated as a swing pump and can be aligned
to either train. The two loops of the SW system are also electrically
independent with two separate divisions of electrical power designated
as the red and green train. The red train power for SW is aligned to
either SW pump 2P4A or SW pump 2P4B, while the green train power is
aligned to either SW pump 2P4C or SW pump 2P4B.
The four power cables associated with the 2P4A, 2P4B, and 2P4C SW
pumps interface with the ``A'' SW intake bay. During plant operations
(Modes 1 through 5), the ANO-2 technical specification requires that
two SW trains be operable. The possible SW pump alignments are SW pumps
2P4A and 2P4B, SW pumps 2P4A and 2P4C, or SW pumps 2P4C and 2P4B. The
power cable arrangements are as follows: conduit EA 1007 contains the
red train power supply cable to SW pump 2P4A; conduit EA2036 contains
the green train power supply cable to swing SW pump 2P4B; and conduit
EA2007 contains the green train power supply cable for SW pump 2P4C.
Conduits EA1007 and EA2036 are protected by separate 1-hour fire-rated
Hemyc fire barriers. Below the 354-foot elevation, these conduits are
also encapsulated in a common galvanized sheet metal moisture barrier.
Conduit EA2007, which is located about 6 feet from the moisture barrier
containing conduits EA1007 and EA2036, is covered by a Thermo-Lag
barrier. The licensee stated that it does not take credit for the
Thermo-Lag barrier to meet the requirements of Appendix R. Conduit
EA1008, which contains the red train power supply to swing SW pump
2P4B, is embedded in the concrete slab at the elevation of 354 feet and
does not enter the bay. Therefore, based on the preceding discussion,
this area would require the addition of fire detectors and an automatic
fire suppression system to comply with the requirements of 10 CFR Part
50, Appendix R, Section III.G.2.c.
The ``A'' SW intake bay contains redundant cables required to
support post-fire safe shutdown. The licensee stated that the 2P4C/2P4B
SW pump combination with SW pump 2P4B aligned to the red train power is
the only pump alignment that would be utilized during normal operations
in Modes 1 through 5 with the ``A'' SW intake bay isolated and drained.
During the recovery from a fire, the time critical function is to
supply cooling water to the diesel generators. The licensee stated
that, on the basis of its calculations, the diesel generators (and
therefore the SW system components) are not required to be operated
during the first 30 minutes of a fire event. The licensee allows the
operators to manually align the SW system because sufficient time is
available to complete the alignment.
Power and control cables for the sluice gates are also located in
the SW intake bays. Sluice gate valves 2CV1470-1, 2CV1472-5, and
2CV1474-2 are normally open, which corresponds to the safe shutdown
position. The redundant control cables are separated horizontally by
approximately 8 feet. As stated previously, the time critical function
of the SW system is to provide cooling to the diesel generators. The
licensee stated that if a fire were to cause the sluice gates to
spuriously close, adequate time would be available before the SW was
required to manually realign any affected component.
The in-situ combustibles in ``A'' SW intake bay and the
administratively allowed quantity of transient combustibles (5 pounds)
do not pose a credible fire threat to the SW pump cables. In the
staff's view, a fire involving transient combustibles in excess of the
administratively allowed quantity is the only type of fire that could
damage redundant SW pump power cables. The licensee has addressed this
threat by protecting both the red train power supply cable for SW pump
2P4A and the green train power supply cable for swing SW pump 2P4B with
1-hour fire-rated barriers, by embedding the red train power supply
cable for SW swing pump 2P4B in concrete, and by administratively
requiring the presence of craft personnel or a fire watch, if the
administrative transient combustible limit is exceeded.
A fire involving transient combustibles could be extinguished by
the craft personnel or the fire watch during its incipient stage. In
the event the fire grows beyond the incipient stage before it is
extinguished, the craft personnel or the fire watch could summon the
plant fire brigade. In addition, the smoke and hot gases would be
directed upwards into the higher elevations of the intake structure,
which are equipped with an automatic fire detection system. Therefore,
in the event that a fire in the intake bay is not discovered by the
craft personnel or the fire watch, it would be detected by the
automatic fire detection system and the plant fire brigade would be
dispatched. If the fire exposes the redundant conduits, the 1-hour
fire-rated barriers and the concrete embedding, with an equivalent 1-
hour fire rating, would provide fire resistive protection, with margin,
for the expected fire hazards and, therefore, provide reasonable
assurance that the power cables would not be damaged before the fire
either burns itself out or is extinguished by the craft personnel, the
fire watch, or the fire brigade. On this basis, the staff concludes
that the existing fire protection design features, coupled with the
administrative controls, provide reasonable assurance that a fire in
the ``A'' SW intake bay would not damage the redundant SW pump power
cables and, therefore, would not adversely affect the ability to
achieve and maintain post-fire safe shutdown. The staff also concludes
that the installation of fire detectors and an automatic fire
suppression system in the area below the 354-foot elevation of the ANO-
2 intake structure would not result in a significant increase in the
level of fire safety for the redundant SW pumps. Additional details
concerning the exemption are provided in the staff's Safety Evaluation
dated October 1, 1999.
For the forgoing reasons, the NRC staff has determined that there
is a low probability of occurrence for a fire event in the ANO-2 intake
structure below the 354-foot elevation. This low probability of
occurrence combined with the lack of combustible material,
administrative controls, and the fire protection features provided, as
stated in the licensee's submittals, is sufficient to reasonably ensure
adequate protection for redundant equipment in the SW system, such that
there is reasonable assurance that at least one means of achieving and
maintaining safe shutdown conditions will remain available during and
after any postulated fire. Therefore, the addition of fire detectors
and an automatic fire suppression system is not necessary to achieve
the underlying purpose of Appendix R, Section III.G.2.c.
The Commission has determined that, pursuant to 10 CFR 50.12, this
exemption is authorized by law, will not endanger life or property or
the common defense and security, and presents no undue risk to public
health and safety. In addition, the Commission has determined that the
special circumstances under 10 CFR 50.12(a)(2)(ii) are present.
Therefore, the Commission hereby grants Entergy Operations, Inc., an
exemption from the requirements of 10 CFR Part 50, Appendix R, Section
III.G.2.c, for the
[[Page 54653]]
area below the 354-foot elevation of the ANO-2 intake structure, such
that fire detectors and an automatic fire suppression system need not
be installed in the fire area.
Pursuant to 10 CFR 51.32, the Commission has determined that the
granting of this exemption will have no significant impact on the
environment (64 FR 52804).
This exemption is effective upon issuance.
Dated at Rockville, Maryland, this 1st day of October 1999.
For the Nuclear Regulatory Commission.
John A. Zwolinski,
Director, Division of Licensing Project Management, Office of Nuclear
Reactor Regulation.
[FR Doc. 99-26143 Filed 10-6-99; 8:45 am]
BILLING CODE 7590-01-P
